knock sensor

nzgemini · Post by **nzgemini** » 16 Oct 2007, 18:13

hey guys just wanted 2 know if any 1 here has fitted a knock sensor 2 the sump of a g200w pics wud b gud cheers

Post by **IZU069** » 17 Oct 2007, 19:30

They should be mounted up near the head. They are usually attached to the inlet manifold.

It may not sense properly if sump mounted - unless you have a knock sensor designed for that.

But maybe other twincammers have done it? I wonder what sensor was used?

archangel62 · Post by **archangel62** » 18 Oct 2007, 22:08

I'm no expert but if I had a knock sensor to install I'd be putting it towards the bottom of the block... Too high and end pistons' signals might be overwhelmed by the closer ones, not sure how these things combat that.. but definitely still into solid metal of the block/head.

Which ECU are you using? I want a knock sensor, but I run MSII and I don't think they're available/affordable yet. Will be soon no doubt.

Post by **IZU069** » 19 Oct 2007, 00:45

Agreed - into solid block or head. But not the sump.
As to high or low - the knocking occurs at head level - ie, combustion.
The near/far doesn't matter as metal conducts sound far better than air etc.

I've seen early version knockers (Chrysler?) mounted mid-block (on the side, half way up), or up top/head (Isuzu).

Mick - for your knock sensor...
Jaycar have a knock sensor kit (KC-5444 $16.95; SiliconChip June 2007) but this excludes the sensor and is designed to be used with the SiliconChip March-June 2007 Programmable Ignition (KC-5442 $89.95 & Ignitor (coil driver) KC-5443 $44.50). I've written about this in another post.

The Jaycar kit is only the band-filter part (4.8-6.4kHz) which feeds into the ProgIgModule - which limits sampling to 6ms after ignition and low RPM (4,000 or 6,000 RPM selectable).
But it wouldn't be difficult to build a circuit triggered from the distributor output which is "active" for 6ms and cuts out above 120Hz (6,000 RPM, 4 cylinders) to feed an EMS assuming it needs this, which is doubtful).

The knock sensor itself is really just a hi-temperature microphone. I was going to experiment with some devices, but the sensors are easy to get from wreckers like Pinch-A-Part.

The June 2007 SiliconChip article is pretty good for knock sensor theory. In summary, a band-filtered microphone to detect knocks (typically 4-7kHz depending on engine) and sampling ONLY during 0-6ms after each detonation (to limit/simplify filtering/detection).
I also have a 330kB pdf from Texas Instruments about using a TMS320 DSP chip for knock detection and analysis. It's real easy if you know your Fourier Transforms and related algebra (yeah, right)!

nzgemini · Post by **nzgemini** » 19 Oct 2007, 17:55

i am running a megasquirt also just wanted 2 c if any1 had done it b4 but im sure il figure out a way 2 get 1 on thanks 4 the help

archangel62 · Post by **archangel62** » 25 Oct 2007, 00:40

Check out the DIYAutotune.com forums. And please, please let me know how you go! I want to do this too!

Which MS you running? I've got Megasquirt II V3.0.